Hi @Martin Vogl ,

The Answer is Yes!! You can change the attestation of a control objective.

But you will have to keep in mind a few things, Provided the Controls are already created already for a respective control Objective ,once you change the Attestation in the control Objective level, it would create controls again but this time with the changed "Attestation" and all of those controls would be in Draft.

Mark my answer correct & Helpful, if Applicable.

Thanks,
Sandeep